scholarly journals Loss of MLKL Decreases Necrotic Core but Increases Macrophage Lipid Accumulation In Atherosclerosis

2019 ◽  
Author(s):  
Adil Rasheed ◽  
Sabrina Robichaud ◽  
My-Anh Nguyen ◽  
Michele Geoffrion ◽  
Mary Lynn Cottee ◽  
...  
Keyword(s):  
Cell Death ◽  
Subcutaneous Administration ◽  
Peritoneal Macrophages ◽  
Necrotic Core ◽  
Endosomal Trafficking ◽  
Lipid Uptake ◽  
Core Formation ◽  
Aortic Sinus ◽  
Cholesterol Levels ◽  
Progression Of Atherosclerosis

ABSTRACTObjectivesDuring the advancement of atherosclerosis, the cellularity of the plaque is governed by the influx of monocyte-derived macrophages and their turnover via apoptotic and non-apoptotic forms of cell death. Previous reports have demonstrated that programmed necrosis, or necroptosis, of macrophages within the plaque contribute to necrotic core formation. Knockdown or inhibition of the necrosome components RIPK1 and RIPK3 slow the progression of atherosclerosis, and activation of the terminal step of necroptosis, MLKL, has been demonstrated in advanced human atherosclerotic plaques. However, whether MLKL directly contributes to lesion development and necrotic core formation has not been investigated.Approaches and ResultsMLKL expression was knocked down in atherogenic Apoe- knockout mice via subcutaneous administration of antisense oligonucleotides (ASO). During advanced atherogenesis, Mlkl knockdown potently reduced cell death in the plaque, with a significant reduction in the necrotic core. However, total lesion area in the aortic sinus remained unchanged. Furthermore, treatment with the MLKL ASO unexpectedly reduced circulating cholesterol levels compared to control ASO, while staining for lipids within the plaque was significantly increased. Peritoneal macrophages transfected with the MLKL ASO showed increased lipid loading upon incubation with modified cholesterol-rich lipoproteins. In lipid-loaded macrophages, MLKL co-localized with Rab7, a marker of the late endosome.ConclusionsThese studies confirm the requirement for MLKL as the executioner of necroptosis, and as such a significant contributor to the necrotic core during atherogenesis. We also identified a previously unknown role for MLKL in interacting with endosomal trafficking components to regulate lipid uptake in macrophages during atherogenesis.

scholarly journals Targeting macrophage necroptosis for therapeutic and diagnostic interventions in atherosclerosis

2016 ◽  
Vol 2 (7) ◽  
pp. e1600224 ◽  
Author(s):  
Denuja Karunakaran ◽  
Michele Geoffrion ◽  
Lihui Wei ◽  
Wei Gan ◽  
Laura Richards ◽  
...  
Keyword(s):  
Cell Death ◽  
Molecular Mechanisms ◽  
Plaque Rupture ◽  
Ex Vivo ◽  
Density Lipoprotein ◽  
Necrotic Core ◽  
Atherosclerotic Plaques ◽  
Core Formation ◽  
Macrophage Cell ◽  
Plaque Instability

Atherosclerosis results from maladaptive inflammation driven primarily by macrophages, whose recruitment and proliferation drive plaque progression. In advanced plaques, macrophage death contributes centrally to the formation of plaque necrosis, which underlies the instability that promotes plaque rupture and myocardial infarction. Hence, targeting macrophage cell death pathways may offer promise for the stabilization of vulnerable plaques. Necroptosis is a recently discovered pathway of programmed cell necrosis regulated by RIP3 and MLKL kinases that, in contrast to apoptosis, induces a proinflammatory state. We show herein that necroptotic cell death is activated in human advanced atherosclerotic plaques and can be targeted in experimental atherosclerosis for both therapeutic and diagnostic interventions. In humans with unstable carotid atherosclerosis, expression of RIP3 and MLKL is increased, and MLKL phosphorylation, a key step in the commitment to necroptosis, is detected in advanced atheromas. Investigation of the molecular mechanisms underlying necroptosis showed that atherogenic forms of low-density lipoprotein increase RIP3 and MLKL transcription and phosphorylation—two critical steps in the execution of necroptosis. Using a radiotracer developed with the necroptosis inhibitor necrostatin-1 (Nec-1), we show that 123I-Nec-1 localizes specifically to atherosclerotic plaques in Apoe−/− mice, and its uptake is tightly correlated to lesion areas by ex vivo nuclear imaging. Furthermore, treatment of Apoe−/− mice with established atherosclerosis with Nec-1 reduced lesion size and markers of plaque instability, including necrotic core formation. Collectively, our findings offer molecular insight into the mechanisms of macrophage cell death that drive necrotic core formation in atherosclerosis and suggest that this pathway can be used as both a diagnostic and therapeutic tool for the treatment of unstable atherosclerosis.

Abstract 3: Targeting Macrophage Necroptosis for Therapeutic and Diagnostic Interventions to Treat Atherosclerosis

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Denuja Karunakaran ◽  
Michele Geoffrion ◽  
Lihui Wei ◽  
Wei Gan ◽  
Ljubica Perisic ◽  
...  
Keyword(s):  
Cell Death ◽  
Molecular Mechanisms ◽  
Plaque Rupture ◽  
Ex Vivo ◽  
Oxidized Ldl ◽  
Combined Treatment ◽  
Necrotic Core ◽  
Core Formation ◽  
Macrophage Cell ◽  
Plaque Instability

Background: Atherosclerosis results from maladaptive inflammation driven primarily by macrophages, whose recruitment and proliferation drive plaque progression. In advanced plaques, macrophage death contributes centrally to the formation of plaque necrosis, which underlies the instability that promotes plaque rupture and myocardial infarction. As such, targeting macrophage cell death pathways may offer promise for the stabilization of vulnerable plaques. Necroptosis is a recently discovered pathway of programmed cell necrosis regulated by RIP3 and MLKL kinases that in contrast to apoptosis, induces a pro-inflammatory state. We hypothesize that atherogenic ligands within the plaque promote macrophage necroptosis and this process underlies necrotic core formation and drives atherosclerotic plaque instability. Results: In humans with unstable carotid atherosclerosis, expression of RIP3 and MLKL is increased and MLKL phosphorylation, a key step in the commitment to necroptosis, is detected in advanced atheromas. Investigation of the molecular mechanisms underlying plaque necroptosis showed that macrophages treated with oxidized LDL have increased expression of necroptotic genes RIP3 and MLKL through ROS-dependent activation of the promoter region and increased RIP3 and MLKL phosphorylation. Combined treatment with oxLDL and DAMPs (damage associated molecular patterns) amplified macrophage necroptotic cell death, indicating that additional inflammatory stimuli present in the lesion could act synergistically to promote necroptosis. Using a radiotracer developed with the necroptosis inhibitor Nec-1, we show that 123 I-Nec1 localizes specifically to atherosclerotic plaques in Apoe-/- mice, and its uptake is tightly correlated to lesion areas by ex vivo nuclear imaging. Furthermore, treatment of Apoe-/- mice with established atherosclerosis with Nec-1 reduced lesion size and markers of plaque instability, including necrotic core formation. Conclusions: Our findings offer molecular insight into the mechanisms of macrophage cell death that drive necrotic core formation in atherosclerosis and suggest that this pathway can be used as both a diagnostic and therapeutic tool for the treatment of unstable atherosclerosis.

scholarly journals Mitochondrial Respiration Is Reduced in Atherosclerosis, Promoting Necrotic Core Formation and Reducing Relative Fibrous Cap ThicknessHighlights

2017 ◽  
Vol 37 (12) ◽  
pp. 2322-2332 ◽  
Author(s):  
Emma P.K. Yu ◽  
Johannes Reinhold ◽  
Haixiang Yu ◽  
Lakshi Starks ◽  
Anna K. Uryga ◽  
...  
Keyword(s):  
Mitochondrial Respiration ◽  
Necrotic Core ◽  
Core Formation ◽  
Fibrous Cap

Abstract 535: Trem Like Transcript-1 (TLT-1) Regulates Both Leukocytes and Endothelial Cells to Mediate Immunohemostasis

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
A. V Washington
Keyword(s):  
Endothelial Cells ◽  
Platelet Activation ◽  
Therapeutic Interventions ◽  
Soluble Form ◽  
Null Mouse ◽  
Aortic Sinus ◽  
Vascular Integrity ◽  
Vessel Growth ◽  
Lewis Lung Carcinoma Model ◽  
Progression Of Atherosclerosis

TLT-1 is a 35kd receptor stored in the α-granules of platelets and released upon platelet activation like p-selectin. A soluble form is also released. A case has been made that the protein or proteins that regulate inflammatory bleeding is stored in the platelet α-granules. We hypothesized that TLT-1 is one of these proteins and we investigated TLT-1’s role in inflammatory bleeding. Using two different models of inflammation and three different models of transmigration we show that TLT-1 mediates neutrophil transmigration across the vessel wall. In the absence of TLT-1 transmigration leads to bleeding that can be partially rescued by soluble TLT-1 (sTLT-1: see poster J. Morales). Based on these results we hypothesized that TLT-1 enhances the progression of atherosclerosis and cancer. To test this hypothesis we crossed the treml1 -/- mice with apoe -/- mice creating the DKO mouse and evaluated lesion progression over 20 weeks. Our results demonstrate that the DKO has significantly less lesions in the aortic sinus than their littermate controls (n=8/group; p <0.05). The smaller lesions are associated with less platelet activation and fewer platelet-leukocyte conjugates. Parallel studies investigating TLT-1 in the α-granules revealed a significant co-localization with pro-angiogenic VEGF and higher sTLT-1 release with PAR1 vs PAR4 platelet activation; suggestive of a role for TLT-1 in angiogenesis. We subsequently asked if, “sTLT-1 has an effect on endothelial cells?” We show angiogenic effects of sTLT-1 on HUVECs that is blocked by the addition of anti-TLT-1, demonstrating it’s a sTLT-1 mediated process. Further studies using the Lewis lung carcinoma model demonstrate that the tumors in the null mouse have significantly fewer vessels than wildtype tumors and lower infiltration of macrophages (n=15). We subsequently show that sTLT-1 partially rescues the phenotype by increasing macrophage infiltration and increasing vessel growth (n=13) and that antibodies to TLT-1 recapitulate the treml1 -/- phenotype (n=10) suggesting anti-TLT-1 may be used as an intervention. We conclude that TLT-1 regulates both leukocytes and endothelial cells to mediate vascular integrity and is a plausible target for therapeutic interventions in cancer and atherosclerosis.

scholarly journals Macrophage insulin receptor deficiency increases ER stress-induced apoptosis and necrotic core formation in advanced atherosclerotic lesions

2006 ◽  
Vol 3 (4) ◽  
pp. 257-266 ◽  
Author(s):  
Seongah Han ◽  
Chien-Ping Liang ◽  
Tracie DeVries-Seimon ◽  
Mollie Ranalletta ◽  
Carrie L. Welch ◽  
...  
Keyword(s):  
Er Stress ◽  
Insulin Receptor ◽  
Necrotic Core ◽  
Core Formation ◽  
Atherosclerotic Lesions ◽  
Induced Apoptosis

scholarly journals Macrophage autophagy regulates mitochondria‐mediated apoptosis and inhibits necrotic core formation in vulnerable plaques

2020 ◽  
Vol 24 (1) ◽  
pp. 260-275 ◽  
Author(s):  
Qingqing Xiao ◽  
Xinyu Che ◽  
Bin Cai ◽  
Zhenyu Tao ◽  
Hengyuan Zhang ◽  
...  
Keyword(s):  
Necrotic Core ◽  
Core Formation ◽  
Vulnerable Plaques

A BRIEF COMMUNICATION

2007 ◽  
Vol 232 (9) ◽  
pp. 1222-1227 ◽  
Author(s):  
Branka Šošic-Jurjević ◽  
Branko Filipović ◽  
Vladimir Ajdžanović ◽  
Dejan Brkić ◽  
Nataša Ristić ◽  
...  
Keyword(s):  
Serum Cholesterol ◽  
Subcutaneous Administration ◽  
Density Lipoprotein ◽  
Male Rats ◽  
Total Serum ◽  
Total Serum Cholesterol ◽  
Middle Aged ◽  
Estradiol Treatment ◽  
Cholesterol Levels ◽  
Higher Doses

Nutritional supplements containing soybean phytoestrogens, the isoflavones genistein (G) and daidzein (D), are increasingly used as alternative therapy for osteoporosis, cancer, and cardiovascular and other diseases with a frequency that increases with advancing age. In this study we examined the effects of subcutaneous administration of either G or D on serum lipid levels in orchidectomized (Orx) and intact (IA) middle-aged male rats, which are experimental models of andropause. Sixteen-month-old Wistar rats were treated with 10 mg/kg and 30mg/kg of either G or D. The control groups received testosterone, estradiol, or vehicle for 3 weeks, after which the total serum cholesterol (TC), low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), and total triglycerides (TT) were measured. Compared with the matching vehicle-treated controls, the higher doses of G and D and testosterone treatment significantly ( P < 0.05) lowered the TC and lipoprotein cholesterol levels. The greatest effect was observed regarding LDL-C in both Orx and IA males after G and D treatments, in which LDL-C decreased by more than 30%. The lower isoflavone doses induced a significant cholesterol-lowering effect ( P < 0.05) only in the Orx group. Like the estradiol treatment, the higher doses of G and D increased the TT levels in both rat models by more than 50% ( P < 0.05). The lower doses of isoflavones increased TT only in the Orx group. In male middle-aged rats, injections of higher doses of G and D decreased the serum cholesterol levels, as did testosterone injection, and brought about an increase in serum triglycerides similar to that observed after estradiol treatment.

scholarly journals Atherogenic characteristics of oral sugar-reducing sulfonylurea derivatives

1994 ◽  
Vol 40 (3) ◽  
pp. 8-10
Author(s):  
M. A. Maxumova ◽  
I. A. Sobenin ◽  
M. I. Balabolkin ◽  
A. N. Orekhov
Keyword(s):  
Peritoneal Macrophages ◽  
Cholesterol Levels ◽  
Murine Peritoneal Macrophages ◽  
Sulfonylurea Drugs

The authors have examined the effects of sulfonylurea drugs glybenclamide and glypizide and of their analogs manilil and minidiab on cholesterol levels in murine peritoneal macrophages. Both glybenclamide and glypizide had a direct atherogenic effect on cultured murine peritoneal macrophages. A similar effect was observed in vivo: blood sera of diabetics after a single intake of 5 mg of manilil or minidiab increased the atherogenic potential of cultured murine peritoneal macrophages.

scholarly journals Site-specific ubiquitination of MLKL targets it to endosomes and targets Listeria and Yersinia to the lysosomes

2022 ◽  
Author(s):  
Seongmin Yoon ◽  
Konstantin Bogdanov ◽  
David Wallach
Keyword(s):  
Cell Death ◽  
Defense Mechanisms ◽  
Kinase Domain ◽  
Intracellular Bacteria ◽  
Endosomal Trafficking ◽  
Polyubiquitin Chains ◽  
Mixed Lineage Kinase ◽  
Lysine Residues ◽  
Covalent Modifications ◽  
Bacterial Yield

AbstractPhosphorylation of the pseudokinase mixed lineage kinase domain-like protein (MLKL) by the protein kinase RIPK3 targets MLKL to the cell membrane, where it triggers necroptotic cell death. We report that conjugation of K63-linked polyubiquitin chains to distinct lysine residues in the N-terminal HeLo domain of phosphorylated MLKL (facilitated by the ubiquitin ligase ITCH that binds MLKL via a WW domain) targets MLKL instead to endosomes. This results in the release of phosphorylated MLKL within extracellular vesicles. It also prompts enhanced endosomal trafficking of intracellular bacteria such as Listeria monocytogenes and Yersinia enterocolitica to the lysosomes, resulting in decreased bacterial yield. Thus, MLKL can be directed by specific covalent modifications to differing subcellular sites, whence it signals either for cell death or for non-deadly defense mechanisms.

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